Valganciclovir and Trimethoprim Interaction
Drug interaction information between Valganciclovir and Trimethoprim.
Valganciclovir and Trimethoprim have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Valganciclovir and Trimethoprim. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Both drugs can cause similar side effects like bone marrow suppression or kidney damage, which increases the risk of these problems when used together.
What To Do
Your doctor should only use these drugs together if the benefits outweigh the risks and will likely monitor your blood counts and kidney function.
FDA Label Information
Other drugs associated with myelosuppression or nephrotoxicity (e.g., adriamycin, dapsone, doxorubicin, flucytosine, hydroxyurea, pentamidine, tacrolimus, trimethoprim/ sulfamethoxazole, vinblastine, vincristine, and zidovudine) Unknown Because of potential for higher toxicity, coadministration with valganciclovir should be considered only if the potential benefits are judged to outweigh the risks.
Valganciclovir Also Interacts With
- Cyclosporine moderate
- Amphotericin B moderate
- Ganciclovir minor
- Probenecid minor
- Bictegravir/Emtricitabine/Tenofovir minor
Trimethoprim Also Interacts With
- Theophylline major
- Prenatal Multivitamin moderate
- Spironolactone moderate
- Spironolactone (Acne) moderate
- Metformin minor
Frequently Asked Questions
Can I take Valganciclovir and Trimethoprim together?
This is a minor interaction. Your doctor should only use these drugs together if the benefits outweigh the risks and will likely monitor your blood counts and kidney function.
How serious is the interaction between Valganciclovir and Trimethoprim?
This interaction is classified as "minor" severity by the FDA. Minor interactions are unlikely to cause significant problems but should still be mentioned to your healthcare provider.
Why do Valganciclovir and Trimethoprim interact?
Both drugs can cause similar side effects like bone marrow suppression or kidney damage, which increases the risk of these problems when used together.
Understanding the Valganciclovir and Trimethoprim Interaction
FDA-approved prescribing information for these two drugs flags their combination as a minor-severity interaction. Valganciclovir belongs to the Antiviral (Nucleoside Analog) class and Trimethoprim belongs to the Dihydrofolate Reductase Inhibitor class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Both drugs can cause similar side effects like bone marrow suppression or kidney damage, which increases the risk of these problems when used together. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Valganciclovir has 8 total documented interactions on file in this dataset, and Trimethoprim has 22. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Your doctor should only use these drugs together if the benefits outweigh the risks and will likely monitor your blood counts and kidney function. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Valganciclovir or Trimethoprim based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.